Air cooling for thermionic tubes



Jan. 21, 1941. J. L. FIN CH 7 2 AIR COOLING FOR THERMIONIC TUBES Qriginai Filed Feb. 17, 1937 2 Sheets-Sheet l,

INVENTOR. JAMES ESL/E F/NCH ATTORNEY.

Jan. 21, 1941-. J. L. FINCH AIR COOLING FOR THERMIONIC TUBES Original m'ea Feb. 17, 19s? F/LA MEN 7' ATTORNEY.

Patented Jan. 21, 1941 UNETED FPTENT OFFICE AIR CUOLING FOR THERMIONIC TUBES .iames Leslie Finch, Patchogue, N. Y., assignor to Radio Corporation of Delaware @riginal application Fe America, a corporation of bruary 17, 1937, Serial No.

a 6 Claims.

This invention relates to anew and novel method for the cooling of metal anodes of thermionic tubes in an effective and efficient manner.

This is a division of my copending application Serial No. 126,124, filed Feb. 17, 1937, now Patent #2,l76,657, patented Oct. 17, 1939.

An object of this invention is to simplify and improve the cooling of thermionic tubes generally by meansof circulating air.

Another object of this invention is to provide an improved air cooling system for the cooling of thermionic tubes having electrical control contacts associated therewith.

Still another object of this invention is to improve the cooling of the vacuum tube by reducing the number of component parts required in a cooling system and thereby reduce the cost thereof.

In the prior art, a vacuum tube was generally cooled by a system employing a liquid medium, such a. system requiring a second cooler for the liquid and numerous insulating connections for carrying the liquid from the point of the source 25 to and around the anode of the tube. When direct air cooling has been used it has been found ineffective and results in a reduction of the allowable output of the tubes.

Briefly. this invention comprises a system 30 having a source of air supply, such as for example, a blower or fan, a chamber, and a supporting means for the tube, the supporting means being arranged with a plurality of curved radiating fins.

The outside contour of the supporting members is in two forms, one being rectangular and the other circular. The circular form provides a more economical unit for the same spacing, although it is not quite as efiicient as the rectangu- 40 lar surface which gives a slightly better cooling, due to the greater surface area of the cooling fins.

Electrical control contacts are located adjacent the cooling system and arranged to break the power supply circuit when undesired temperatures are reached.

This invention will best be understood by referring to the accompanying drawings, in which:

Fig. 1 is a sectional View of an improved air cooling system;

Fig. 2 is a sectional view of another embodiment of this invention;

Fig. 3 is a plan View of Fig. 1, showing a circular support and air chamber;

Fig. 4 is a detail of an improved cooling vane;

Fig. 5 is a sectional view of a still further embodiment of a cooling arrangement; and

Fig. 6 is a sectional detail of a thermostatic switch actuating device.

Referring now in detail to the drawings, I is a metal anode of a thermionic tube, 2 indicates its glass envelope, 3 is the grid leads and t and 5 the cathode and filament leads. Anode l is sealed into a suitable cavity formed in a metallic block members can be removed with the tube when it is necessary to change the tube. Hub member 9 is provided with an extra large outer diameter. This provides a massive metal hub having a cross-section greater than block 6, which allows heat generated in anode I to travel through it to the ends of a large number of cooling fins I3 with a minimum temperature drop. The fins 13 are soldered into slots in the periphery of hub 9 and leave the slots in approximately a radial di- I rection, and are also curved so as to keep the space between adjacent fins approximately parallel or equal throughout their length, which arrangement gives an increased cooling area, and also maintains the air friction between the fins approximatelythe same throughout the whole sectional area of the cooling system. The outer ends of the fins are secured to an enclosing and supporting member M; as mentioned above, this may be rectangular or circular in form. A fan E5, driven by a motor It, forces air upward and around the fins l3, thus carrying away the heat generated in anode I. Surrounding the fan is a duct or container 11, which may be of metal or transparent insulating material, such as glass. The lower end of i1 is preferably of circular section and fits closely around the blades of the fan I5, or, in the case of a blower, around the manifold. The upper end of duct I1 is of a section corresponding to that of the outside contour of supporting member 14. The spacing between members I4 and I1 is enclosed by a duct l8, made preferably of insulating material, having the requisite insulating characteristics for withstanding the voltage normally placed upon the member l4 and also being of suitable size for confining the stream of air from the fan so that the most of it passes through the cooling fin area.

Member 18 is removable, at least in part, to allow replacement of tubes, and it is preferable that member It be made of glass or other transparent insulating material, in order that the inside be visible. The filament leads l and 5 are preferably brought out through bushings in the walls of member ll, while the grid lead 3 is brought out through an aperture in member 18.

Associated with the cooling unit, is an air fiow trip l9 which closes a circuit between member l9 and contact 20, when the force of air reaches above that of a predetermined value, and allows the circuit to open when the fiow is below a predetermined value. A thermostat 2! is also associated with member I l and is located in such a position that with or without the fan running normally, any excess in temperature will cause the circuit between members 2! and 22' to open, while normal temperatures will allow this circuit toremain closed. These two circuit devices are so connected in the electrical circuit that the power will be removed from the device in the ,5 case of failure of the cooling air, or in the case of an excess temperature due to any cause.

The modification shown in Fig. 2 is generally similar to that of Fig. 1, except that the air duct [8 can be dispensed with for the reason that the area of the fin section is tapered outwardly toward the top, the upper area being greater Where the air leaves than where it enters. A blast of air from the fan directed against the intake of the fins has stored in it kinetic energy, and as this air passes through the expanding fin area its velocity decreases and therefore emerges at a reduced velocity. This decrease in velocity represents a transfer of energy and this transfer is arranged so as to be substantially wfsufiicient to supply the energy required to overcome the friction of air passing between the fins 13; thus, no difference in pressure is required to force the air through the fins and therefore,

essentially all of the air directed to the fins will 45 pass through them, whereas without this taper,

the pressure would have to be greater at the intake than at the exhaust. Since the exhaust pressure will be atmospheric, the intake will have to be above atmospheric. This would result in 60 only a part of the air from the fan !5 passing through the fins, if the ducts I"! and I8 were omitted.

An improved cooling or radiating member is shown in detail in Fig; 4. The vanes 29 are pro- 55 vided to give substantially equal spacing by the use of a non-uniform curve. It will be noted that from a desired distance from the anodes, the vanes run substantially parallel, at which point the most effective cooling is obtained. By 60 the use of the non-uniform curved vane, a greater cooling of the tube can be obtained for the same amount of space and air pressure than if the cooling fins or vanes were arranged radially. A further modification of cooling arrangement 5 is shown in Fig. 5. This arrangement is similar to that of Fig. 1, except that the fan has been placed over the cooling fin assembly and air is drawn up past the cooling fins and then through 70 the fan. The enclosing duct is placed between the fan and the fin assembly, as in Fig. 1. This arrangement also makes it possible to filterthe cooling air by providing an air filter 3d and makes it possible to direct the air discharged 75 from the unit into a duct which can be arranged to carry the air to the outside, if the transmitting apparatus is located inside a building.

The thermostat element 2| is arranged to be responsive to the temperature of the air leaving the fin assembly. However, in order to have a more accurate control of the temperature at the very point where the heat is generated, an additional modification is made to provide a thermostat element which is responsive to the temperatures of the hub, itself, and electrically connected to the hub. This thermostat element is indicated as 3|, and is provided with a cord 32 which terminates in a snap switch 33, having a spring 34, also maintaining the switch under tension, and in the operating position contacts 35 and 3B are normally closed by switch blade 33. By means of this thermostatic arrangement, the electrical contacts are essentially at ground potential, while the actuating thermostatic element is subjected to the anode potential. In place of the string member 32, a strip of insulating material can be provided.

Fig. 6 shows a sectional detail of the new and novel thermostat element and comprises a tapered aperture 31 in which a metallic plug 38 is driven.

A metal rod 39 is retained within member 33 by means of a low melting point solder, such as Woods metal. In case of excessive heat in hub member 26, the solder fuses and allows the metallic member 39 to move due to the tension of spring 34 andthus break the circuits and actuate the lock contacts which remove the power from the tube. When the unit has cooled, the solder again solidifies and it is necessary to reinsert member 39 so that it corresponds to the original position.

While only a few modifications of this invention have been disclosed, it is to be distinctly understood that it is capable of taking other forms within the spirit and scope thereof.

What is claimed is:

1. A cooling system comprising an electron discharge device having at least an anode and cathode, a metallic hub member surrounding said anode, a rectilinear shaped metallic band surrounding said hub member, a plurality of radiating fins radially extending outward from said metallic hub member to join said band, each fin being curved to be of a greater length than the shortest radial distance between the hub and said metallic band, means comprising a rotatable device for supplying cooling air to said electron discharge device, said device located adjacent said metallic hub member. a

2. A cooling system comprising an electron discharge device having at least an anode and cathode, a metallic sleeve surrounding said anode, a circular metallic hub member surrounding said sleeve, a square shaped metallic band surrounding said hub member, a plurality of slots in said hub member, a plurality of radiating fins extending outward from said hub member to join said band, each fin being curved to be of a greater length than the shortest radial distance between the hub and said metallic band and located on said circular metallic hub member to be spaced apart from each other in a substantially equal distance, said metallic band supported to and connect ing the outside ends of said fins, and means including a rotatable device for supplying cooling air to said electron discharge device; said Totatable device located adjacent said metallic hub member.

3. A cooling system comprising an electron discharge device having at least an anode and a cathode, a metallic hub member surrounding said anode. a rectilinear metallic band surrounding said hub member, a plurality of radiating fins extending outward from said metallic hub memher and joining said metallic band, each one of said fins being bent to be of a greater length than the shortest radial distance between said hub member and said metallic band, and means comprising a rotatable device for supplying cooling air to said electron discharge device.

4. A cooling system comprising an electron discharge device having at least an anode and a cathode, a metallic hub member surrounding said anode, a square shaped metallic band surrounding said hub member, a plurality of radiating fins extending outward from said metallic hub member and joining said metallic band, each one of said fins being bent to be of a greater length than the shortest radial distance between said hub member and said metallic band, and a seemember, means comprising a rotatable device for supplying cooling air to said electron dis charge device, said rotatable device located within the confines of said second band member.

5. An air cooled thermionic tube comprising means for transferring heat from said tube to the surrounding air, a plurality of fins, a central hub member. a rectilinear shaped metallic band surrounding said hub member, each fin being curved to be of a greater length than the shortest radial distance between the hub and discharge device having at least an anode and "cathode, a metallic hub member surrounding said anode, a rectilinear shaped metallic band surrounding said hub member, a plurality of radiating fins radially extending outward from said metallic hub member to join said band, each fin being curved to be of a diiferent length than that and band member located adjacent said first band of an adjacent fin, and means comprising a rotatable device for supplying air to said electron discharge device, said device located adjacent said metallic hub member.

JAMES LESLIE FINCH.

Lil 

